(1) Field of the Invention
The invention relates to an physiological signal measurement system, and especially relates to a signal measurement and feedback system for real-time photoplethysmograph.
(2) Description of the Prior Art
Generally speaking, for the purpose of measuring physiological signal such as photoplethysmograph, two conventional sensing methods are popularly adopted: fingertip clip sensor module and finger ring sensor module. A typical fingertip clip sensor module mainly comprises a pair of shanks, which are crisscross pivotal jointed in respective middle section in scissors-like manner such that each shank serves as a prong of an integrated fingertip clip sensor module. Each shank includes a front jaw and a rear levering stem in addition to the middle pivotal section, which acts as a fulcrum at the pivotal joint. One front jaw of a shank contains a light-emitting diode (LED) while the other front jaw of another shank contains light sensing receiver such as photocell, photodiode or the like so that the pair of front jaws forms a sensor module. The pair of rear levering stems are lightly spring-propped so that the pair front jaws remain in close status if in idle mode while the pair front jaws can be opened and comfortably clip a finger of the examinee in loosely clamping manner without any painful pinch feeling in operation mode. In this operation mode, the front jaw with light-emitting diode (LED) will illuminate light beam to pass through the finger of the examinee to reach the other front jaw with light sensing receiver, which perceives brightness fluctuation of received light beam in conformity with variance of the blood content in the finger.
The typical fingertip clip sensor module can be further adapted into various shapes, but all of them have common easily drop off drawback. Because the fingertip clip sensor module can only loosely clamp the finger of the examinee to assure a comfortably clip without any painful pinch feeling in operation mode, it is easily dropped off due to inadvertently pull and drag or sudden movement of the examinee. To overcome foregoing drawback of the fingertip clip sensor module, the finger ring sensor module is introduced into measurement of the physiological signal such as photoplethysmograph. The finger ring sensor module comprises a ring-shaped holder, which includes a light-emitting diode (LED) and a light sensing receiver such as photocell, photodiode or the like respectively juxtaposed in opposed sides therein, so that the finger ring holder is used as an integral sensor module. In practical usage, the examinee just snugly wears the finger ring holder of the finger ring sensor module onto the finger, the light-emitting diode (LED) therein will illuminate light beam to pass through the finger of the examinee to reach the light sensing, receiver therein, which perceives brightness fluctuation of received light beam in conformity with variance of the blood content in the finger. Though the finger ring sensor module solves the easily drop off drawback of the fingertip clip sensor module, but it creates another drawback that no universal ring size can meet various finger dimensions of different examinees. Besides, the perceived brightness fluctuation from either fingertip clip sensor module or finger ring sensor module can be further well conditioned by a suite of measuring devices and relayed to display in related medical monitor in combination as a meaningful physiological signal. Thus, by means of foregoing operation, the fingertip clip sensor module and finger ring sensor module can be used to acquire suitable physiological signal such as photoplethysmograph of the examinee to be interpreted by medical personnel for diagnostic and pathological usage.
However, the foregoing suite of measuring devices and medical monitor for conditioning the perceived brightness fluctuation form the fingertip clip sensor module and finger ring sensor module is always bulky and complicated in association, which confines the application being limited in clinical usage and cumbersome unable for daily living usage outside of clinics. To solve issue mentioned above, a light and portable headphone sensor module is invented. For example, a patent title of “Measuring headphone of heart rate variability” in Taiwan Patent No. 201036591 contrives the measuring headphone containing a sensor module with a light-emitting diode (LED) and a light sensing receiver such as photocell, photodiode or the like embedded therein. In practical usage, the examinee just snugly wears the measuring headphone containing the sensor module onto the head, the light-emitting diode (LED) therein will illuminate light beam to reflect from the auricular blood of the examinee to backwardly reach the light sensing receiver therein, which perceives brightness fluctuation of received light beam in conformity with variance of the blood content in the finger. In this optical aspect of reflecting light beam from the auricular blood, time headphone sensor module is classified as reflective sensor module category while both of the fingertip clip sensor module and finger ring sensor module, which apply the same optical principle in passing light beam through finger, are classified as transmissive sensor module category. For sensitivity comparison, the brightness fluctuation signal of the reflective sensor module category is much weaker than that of the transmissive sensor module category so that the reflective sensor module category is much more vulnerably affected by the noise interference such as motion artifact than the transmissive sensor module category.
In conclusion, the drawbacks of foregoing conventional sensor modules are summarized as below. For fingertip clip sensor module, it has easily dropping off drawback and cumbersome drawback in associated suite of measuring devices and medical monitor. For fingertip ring sensor module, it has drawback in no universal ring size able to meet various finger dimensions of different examinees in addition of cumbersome drawback in associated suite of measuring devices and medical monitor. For headphone sensor module, it has drawback in being vulnerably affected by the noise interference of motion artifact. Therefore, how to simultaneously solve all the drawbacks of three foregoing conventional sensor modules of physiological signal having features of high functional usage with obviation of noise interference and low power consumption during practical operation becomes an urgent problem in the technical field of the present invention.